A waste heat recovery system of an internal combustion engine has a Rankine cycle circuit. The Rankine cycle circuit includes a circulation path through which heat-transfer media are circulated. A pump, a heat exchanger, an expander and a condenser are interposed in the circulation path in the order named. In the heat exchanger, the heat-transfer media are heated by using the heat released from the internal combustion engine, and the heat-transfer media that have been heated are expanded within the expander. In this process, power is supplied through the rotary shaft of the expander, and is used as regenerative energy.
As to the heat engine disclosed in Patent Document 1, for example, the engine is aided by regenerative energy. To be specific, the rotary shaft of the expander and that of the engine are coupled together through a transmission and a clutch, and the rotation of the expander's rotary shaft is transmitted to the engine's rotary shaft at a predetermined transmission gear ratio. In the waste heat recovery system of the Rankine engine and that of the internal combustion engine disclosed in Patent Documents 2 and 3, respectively, the expander's rotary shaft and the generator's rotary shaft are coupled together, and regenerative energy is converted into electric power by the generator.
Patent Documents 2 and 3 provide working-medium blocking means and a valve system, respectively, in the upstream of their respective expanders. More specifically, in the Rankine engine of Patent Document 2, bypass blocking means is placed side by side with the working-medium blocking means. At the time of starting the Rankine engine, the working-medium blocking means is first opened. The bypass blocking means is not opened until a differential pressure between the expander's inlet and outlet becomes equal to or higher than a preset value. When the Rankine engine is to be stopped, the bypass blocking means is first opened, and then, the working-medium blocking means is closed at the time point when the differential pressure between the expander's inlet and outlet becomes equal to or lower than the preset value. This is supposed to make it possible to achieve safe start and stop operations.
The waste heat recovery system of an internal combustion engine described in Patent Document 3 determines that there is an abnormality whenever a control signal of the generator strays from a target control zone. In such a case, a liquid pump is halted, and only predetermined switching devices are turned on. The valve system is then closed, which completely stops the influx of working fluid into the expander. On this account, it is considered that the expander and the generator can be stopped even if the rotation control of the generator becomes impossible.    Patent Document 1: Kokai No. 57-99222 (FIG. 1, for example)    Patent Document 2: Kokai No. 59-138707 (page 3, upper left column to lower left column and FIGS. 4 to 6, for example)    Patent Document 3: Kokai No. 2006-170185 (FIG. 1 and Pars. 0093 to 0096, for example)